Memory Array with Bit-Lines Connected to Different Sub-Arrays Through Jumper Structures

ABSTRACT

An integrated circuit structure includes an SRAM array including a first sub-array having a first plurality of rows and a plurality of columns of SRAM cells, and a second sub-array having a second plurality of rows and the plurality of columns of SRAM cells. A first bit-line and a first complementary bit-line are connected to the first and the second pass-gate MOS devices of SRAM cells in a column in the first sub-array. A second bit-line and a second complementary bit-line are connected to the first and the second pass-gate MOS devices of SRAM cells in the column in the second sub-array. The first bit-line and the first complementary bit-line are disconnected from the second bit-line and the second complementary bit-line. A sense amplifier circuit is electrically coupled to, and configured to sense, the first bit-line, the first complementary bit-line, the second bit-line, and the second complementary bit-line.

PRIORITY CLAIM AND CROSS-REFERENCE

This application is a continuation of U.S. patent application Ser. No.15/601,445, entitled “Memory Array with Bit-Lines Connected To DifferentSub-Arrays Through Jumper Structures,” filed on May 22, 2017, which is acontinuation of U.S. patent application Ser. No. 15/061,573, entitled“Memory Array with Bit-Lines Connected To Different Sub-Arrays ThroughJumper Structures,” filed on Mar. 4, 2016, now U.S. Pat. No. 9,659,635issued May 23, 2017, which application claims the benefit of thefollowing provisionally filed U.S. Patent application: Application Ser.No. 62/288,811, filed Jan. 29, 2016, and entitled “High Speed MemoryChip,” which applications are hereby incorporated herein by reference.

BACKGROUND

Static Random Access Memory (SRAM) is commonly used in integratedcircuits. SRAM cells have the advantageous feature of holding datawithout a need for refreshing. With the increasing demanding requirementto the speed of integrated circuits, the read speed and write speed ofSRAM cells also become more important. With the increasinglydown-scaling of the already very small SRAM cells, however, such requestis difficult to achieve. For example, the sheet resistance of metallines, which form the word-lines and bit-lines of SRAM cells, becomesincreasingly higher, and hence the RC delay of the word lines andbit-lines of SRAM cells is increased, preventing the improvement in theread speed and write speed.

When entering into nanometer era, SRAM cells are made very large toincrease the SRAM cell efficiency. This, however, incurs two problems.Firstly, each bit-line has to be connected to more rows of SRAM cells,which induces higher bit-line metal coupling capacitance, and hence thedifferential speed of the differential bit-lines (bit-line and bit-linebar) is reduced. Secondly, each word-line also has to be connected tomore columns of SRAM cells, resulting in longer word-lines and henceworsened resistance and increased RC delay.

BRIEF DESCRIPTION OF THE DRAWINGS

Aspects of the present disclosure are best understood from the followingdetailed description when read with the accompanying figures. It isnoted that, in accordance with the standard practice in the industry,various features are not drawn to scale. In fact, the dimensions of thevarious features may be arbitrarily increased or reduced for clarity ofdiscussion.

FIGS. 1 and 2 illustrate circuit diagrams of a Static Random AccessMemory (SRAM) cell in accordance with some embodiments.

FIG. 3 illustrates a cross-sectional view of the layers involved in anSRAM cell array in accordance with some embodiments.

FIG. 4 illustrates a layout of front-end features of an SRAM cell inaccordance with embodiments.

FIG. 5 illustrates an SRAM array including two sub-arrays in accordancewith some embodiments.

FIG. 6 illustrates complementary bit-lines and a CVdd line connected totwo sub-arrays in accordance with some embodiments.

FIG. 7 illustrates a layout of an SRAM cell in accordance with someembodiments.

FIG. 8 illustrates an SRAM array including two sub-arrays in accordancewith some embodiments.

FIG. 9 illustrates complementary bit-lines and two CVdd lines connectedto two sub-arrays in accordance with some embodiments.

DETAILED DESCRIPTION

The following disclosure provides many different embodiments, orexamples, for implementing different features of the invention. Specificexamples of components and arrangements are described below to simplifythe present disclosure. These are, of course, merely examples and arenot intended to be limiting. For example, the formation of a firstfeature over or on a second feature in the description that follows mayinclude embodiments in which the first and second features are formed indirect contact, and may also include embodiments in which additionalfeatures may be formed between the first and second features, such thatthe first and second features may not be in direct contact. In addition,the present disclosure may repeat reference numerals and/or letters inthe various examples. This repetition is for the purpose of simplicityand clarity and does not in itself dictate a relationship between thevarious embodiments and/or configurations discussed.

Further, spatially relative terms, such as “underlying,” “below,”“lower,” “overlying,” “upper” and the like, may be used herein for easeof description to describe one element or feature's relationship toanother element(s) or feature(s) as illustrated in the figures. Thespatially relative terms are intended to encompass differentorientations of the device in use or operation in addition to theorientation depicted in the figures. The apparatus may be otherwiseoriented (rotated 90 degrees or at other orientations) and the spatiallyrelative descriptors used herein may likewise be interpretedaccordingly.

A Static Random Access Memory (SRAM) cell and the corresponding SRAMarray are provided in accordance with various exemplary embodiments.Some variations of some embodiments are discussed. Throughout thevarious views and illustrative embodiments, like reference numbers areused to designate like elements.

FIG. 1 illustrates a circuit diagram of SRAM cell 10 in accordance withsome embodiments. SRAM cell 10 includes pull-up transistors PU-1 andPU-2, which are P-type Metal-Oxide-Semiconductor (PMOS) transistors, andpull-down transistors PD-1 and PD-2 and pass-gate transistors PG-1 andPG-2, which are N-type Metal-Oxide-Semiconductor (NMOS) transistors. Thegates of pass-gate transistors PG-1 and PG-2 are controlled by word-lineWL that determines whether SRAM cell 10 is selected or not. A latchformed of pull-up transistors PU-1 and PU-2 and pull-down transistorsPD-1 and PD-2 stores a bit, wherein the complementary values of the bitare stored in Storage Date (SD) node 110 and SD node 112. The stored bitcan be written into, or read from, SRAM cell 10 through complementarybit lines including bit-line (BL) 114 and bit-line bar (BLB) 116. SRAMcell 10 is powered through a positive power supply node Vdd that has apositive power supply voltage (also denoted as VDD). SRAM cell 10 isalso connected to power supply voltage VSS (also denoted as Vss), whichmay be an electrical ground. Transistors PU-1 and PD-1 form a firstinverter. Transistors PU-2 and PD-2 form a second inverter. The input ofthe first inverter is connected to transistor PG-1 and the output of thesecond inverter. The output of the first inverter is connected totransistor PG-2 and the input of the second inverter.

The sources of pull-up transistors PU-1 and PU-2 are connected to CVddnode 102 and CVdd node 104, respectively, which are further connected topower supply voltage (and line) Vdd. The sources pull-down transistorsPD-1 and PD-2 are connected to CVss node 106 and CVss node 108,respectively, which are further connected to power supply voltage/lineVss. The gates of transistors PU-1 and PD-1 are connected to the drainsof transistors PU-2 and PD-2, which form a connection node that isreferred to as SD node 110. The gates of transistors PU-2 and PD-2 areconnected to the drains of transistors PU-1 and PD-1, which connectionnode is referred to as SD node 112. A source/drain region of pass-gatetransistor PG-1 is connected to bit line BL 114 at a BL node. Asource/drain region of pass-gate transistor PG-2 is connected to bitline BLB 116 at a BLB node.

FIG. 2 illustrates an alternative circuit diagram of SRAM cell 10,wherein transistors PU-1 and PD-1 in FIG. 1 are represented as firstinverter Inverter-1, and transistors PU-2 and PD-2 are represented assecond inverter Inverter-2. The output of first inverter Inverter-1 isconnected to transistor PG-1 and the input of the second inverterInverter-2. The output of second inverter Inverter-2 is connected totransistor PG-2 and the input of second inverter Inverter-2.

FIG. 3 illustrates a schematic cross-sectional view of a plurality oflayers involved in SRAM cell 10, which layers are formed on asemiconductor chip or wafer. It is noted that FIG. 3 is schematicallyillustrated to show various levels of interconnect structure andtransistors, and may not reflect the actual cross-sectional view of SRAMcell 10. The interconnect structure includes a contact level, an OD(wherein the term “OD” represents “active region”) level, via levelsVia_0 level, Via_1 level, Via_2 level, and Via_3 level, and metal-layerlevels M1 level, M2 level, M3 level, and M4 level. Each of theillustrated levels includes one or more dielectric layers and theconductive features formed therein. The conductive features that are atthe same level may have top surfaces substantially level to each other,bottom surfaces substantially level to each other, and may be formedsimultaneously. The contact level may include gate contacts (alsoreferred to as contact plugs) for connecting gate electrodes oftransistors (such as the illustrated exemplary transistors PU-1 andPU-2) to an overlying level such as the Via_0 level, and source/draincontacts (marked as “contact”) for connecting the source/drain regionsof transistors to the overlying level.

FIG. 4 illustrates a layout of the front-end features of SRAM cell 10 inaccordance with exemplary embodiments, wherein the front-end featuresincludes the features in the Via_0 level (FIG. 1) and the levelsunderlying the Via_0 level. The outer boundaries 10A, 10B, 10C, and 10Dof SRAM cell 10 are illustrated using dashed lines, which mark arectangular region. An N_well region is at the middle of SRAM cell 10,and two P_well regions are on opposite sides of the N_Well region. CVddnode 102, CVdd node 104, CVss node 106, CVss node 108, the bit-line (BL)node, and the bit-line bar (BLB) node, which are shown in FIG. 1, arealso illustrated in FIG. 4. Gate electrode 16 forms pull-up transistorPU-1 with the underlying active region (in the n-well region) 20, whichmay be fin-based, and hence are referred to fin 20 hereinafter. Gateelectrode 16 further forms pull-down transistor PD-1 with the underlyingactive regions (in the first P_well region on the left side of theN_well region) 14, which may be fin-based. Gate electrode 18 formspass-gate transistor PG-1 with the underlying active region 14. Gateelectrode 36 forms pull-up transistor PU-2 with the underlying activeregion (in the n_well region) 40. Gate electrode 36 further formspull-down transistor PD-2 with the underlying active region (in thesecond P_well region on the right side of the N_well region) 34. Gateelectrode 38 forms pass-gate transistor PG-2 with the underlying activeregion 34. In accordance with some embodiments of the presentdisclosure, pass-gate transistors PG-1 and PG-2, pull-up transistorsPU-1 and PU-2, and pull-down transistors PD-1 and PD-2 are FinField-Effect Transistors (FinFETs). In accordance with alternativeembodiments of the present disclosure, pass-gate transistors PG-1 andPG-2, pull-up transistors PU-1 and PU-2, and pull-down transistors PD-1and PD-2 are planar MOS devices.

FIG. 4 illustrates two fins 14 (and two fins 34) in accordance with someembodiments. In accordance with other embodiments, there may be a singlefin, two fins, or three fins, wherein one of the fins 14 (and one offins 34) is illustrated as dotted to indicate the additional fins thatmay or may not exist.

As shown in FIG. 4, SD node 110 includes source/drain contact plug 42and gate contact plug 44, which are the features at the contact level(FIG. 2). Contact plug 42 is elongated and has a longitudinal directionin the X direction, which is parallel to the extending directions ofgate electrodes 16 and 36. Gate contact plug 44 comprises a portionover, and is electrically connected to, gate electrode 36. In accordancewith some embodiments of the present disclosure, gate contact plug 44has a longitudinal direction in the Y direction, with is perpendicularto the X direction. In the manufacturing of the SRAM cell 10 on physicalsemiconductor wafers, contact plugs 42 and 44 may be formed as a singlecontinuous butted contact plug.

SD node 112 includes source/drain contact plug 46 and gate contact plug48. Gate contact plug 48 has a portion overlapping source/drain contactplug 46. Since SD node 110 may be symmetric to SD node 112, the detailsof gate contact plug 48 and source/drain contact plug 46 are notrepeated herein, and may be found referring to the discussion of gatecontact plug 44 and source/drain contact plug 42, respectively.

FIG. 4 also illustrates word line contacts (marked as WL contacts)connected to gate electrodes 18 and 38. Furthermore, a plurality ofvias, each illustrated using a circle and a “x” sign in the circle, isover and contacting the respective underlying contact plugs. Elongatedcontact plugs 54A and 54B are used to connect to the source regions ofpull-down transistors PD-1 and PD-2, respectively, to CVss lines.Elongated contact plugs 54A and 54B are parts of the CVss-nodes 106 and108, respectively. Elongated contact plugs 54A and 54B have lengthwisedirections parallel to the X direction, and may be formed to overlap thecorners of SRAM cell 10. Furthermore, elongated contact plugs 54A and54B may further extend into neighboring SRAM cells that abut SRAM cell10.

FIG. 5 illustrates schematic view of SRAM array 56 and related circuits.The illustrated schematic SRAM array 56 includes 8 rows and 4 columns tosimplify the explanation of the embodiments. The actual SRAM array 56may have a greater number of rows and columns. For example, the numberof rows may be 64, 128, 256, 512, or more, and the number of columns mayalso be 64, 128, 256, 512, or more. The SRAM cells in SRAM array 56 mayhave the structure shown in FIGS. 1, 2, and 4. Some exemplary SRAM cells10 in SRAM array 56 are marked.

SRAM array 56 is divided into two sub-arrays 56A and 56B, which areseparated from each other by jumper structure 58. Sub-arrays 56A and 56Bhave different rows and same columns. For example, When SRAM array 56 isa 256×256 array, sub-array 56A has rows 1 through 128, and columns 1through 256. Sub-array 56B has rows 129 through 256, and the samecolumns 1 through 256. Jumper structure 58 includes a plurality of strapcells, each in one column of SRAM array 56. One of strap cells 47 isillustrated. The lengths (in the row direction, which is shown as Xdirection) of the strap cells are the same as the lengths of therespective columns. Strap cells (and hence the jumper structure 58) haveno SRAM cells formed therein. In accordance with some embodiments of thepresent disclosure, a plurality of word-lines 60 and 62 (marked as60/62) are placed in pairs in the row direction, with each pair ofword-lines 60 and 62 extending into one row of SRAM cells 10. Word-lines60 and 62 are connected to word-line driver 43, which providesappropriate word-line signals for selected and un-selected rows. Inaccordance with alternative embodiments of the present disclosure, wordline 60 is formed, while word-line 62 is not formed. Word-line 60 may beformed in the M2 level (FIG. 3), and word-line 62 may be formed in theM4 level, as also shown in FIG. 7. Furthermore, each of word-lines 60and 62 extends all the way through the entirety of the respective row,and is connected to CVdd nodes 102 (FIGS. 1 and 4) of all SRAM cells 10in the respective row.

Sub-array 56A includes a plurality of pairs of complementary bit-linesincluding bit-lines 114A (which correspond to BL 114 in FIG. 1) andtheir complementary bit-lines 116A (which correspond to BLB 116 in FIG.1). Bit-lines 114A and 116A extend in the column direction. Thecomplementary bit-lines are used to carry complementary bit-linesignals. Each of bit-lines 114A is connected to the drain regions ofpass-gate transistors PG-1 (FIG. 1) in the respective column of SRAMcells 10 in sub-array 56A. Each of bit-lines 116A is connected to thedrain regions of pass-gate transistors PG-2 (FIG. 1) in the respectivecolumn of SRAM cells 10 in sub-array 56A. In accordance with someembodiments of the present disclosure, bit-lines 114A and 116A are in alow metal layer such as M1 level/layer (FIG. 3).

Sub-array 56B includes a plurality of pairs of complementary bit-linesincluding bit-lines 114B (which correspond to BL 114 in FIG. 1) andtheir complementary bit-lines 116B (which correspond to BLB 116 in FIG.1). Bit-lines 114B and 116B extend in the column direction. Each ofbit-lines 114B is connected to the drain regions of pass-gatetransistors PG-1 (FIG. 1) in the respective column of SRAM cells 10 insub-array 56B. Each of bit-lines 116B is connected to the drain regionsof pass-gate transistors PG-2 (FIG. 1) in the respective column of SRAMcells 10 in sub-array 56B. In accordance with some embodiments of thepresent disclosure, bit-lines 114B and 116B are also in a low metallayer such as M1 level/layer (FIG. 3).

FIG. 6 illustrates a schematic view of the bit-lines 114A, 114B, 116A,and 116B that are in the same column of SRAM array 56. The illustratedportion may be in the region marked using a rectangular box 45 in FIG.5. The structure shown in FIG. 6 is repeated for each of the columns, asalso shown in FIG. 5. Referring to FIG. 6, bit-lines 114B and 116B areconnected to input nodes 68A and 68B, respectively, of multiplexer MUX.Bit-lines 114A and 116A are connected to metal lines 66, which arefurther connected to input nodes 70A and 70B. Accordingly, bit-lines114A and 116A are also electrically connected to input nodes 70A and70B, respectively. The connection between bit-lines 114A and 116A andthe respective metal lines 66 are through connection modules 65. Metallines 66 cross over, without being connected to, sub-array 56B (FIG. 5).Alternatively stated, although metal lines 66 cross over sub-array 56B,metal lines 66 are not connected to the underlying SRAM cells 10 insub-array 56B. Accordingly, metal lines 66 are alternatively referred toas bridging lines throughout the description. As also shown in FIG. 5,bridging lines 66 terminate in jumper structure 58, and may terminate inthe respective strap cells separating the SRAM cells in sub-array 56Afrom the SRAM cells in sub-array 56B.

Bit-lines 114A and 114B are physically disconnected from each other.Although in the same column of SRAM array 56, bit-lines 114A and 114Bare electrically disconnected from each other, and are configured tocarry different signals in the operation of SRAM array 56. Similarly,Bit-lines 116A and 116B are physically disconnected from each other.Although in the same column of SRAM array 56, bit-lines 116A and 116Bare electrically disconnected from each other, and are configured tocarry different signals in the operation of SRAM array 56.

As shown in FIGS. 5 and 6, multiplexer MUX is connected to control unit72, which provides enable control signals to operate multiplexer MUX, sothat either the signals on bit-lines 114A and 116A are selected, and areforwarded to output nodes 74 of multiplexer MUX, or the signals onbit-lines 114B and 116B are selected, and are forwarded to output nodes74. At one time, at most one of the complementary pairs 114A/116A and114B/116B is selected by multiplexer MUX. The selected signals on eitherbit-line pair 114A/116A or bit-line pair 114B/116B are provided to senseamplifier circuit 76.

Since bit-lines 114A and 116A are connected to sub-array 56A, but not tosub-array 56B, and bit-lines 114B and 116B are connected to sub-array56B, but not to sub-array 56A, regardless of whether bit-line pair114A/116A is selected or bit-line pair 114B/116B is selected, theselected bit-line pair is connected to a half of the SRAM cells in theselected column. When a row in sub-array 56A is selected for readoperation, bit-lines 114A and 116A are selected, and their signals areoutput to output nodes 74. Similarly, when a row in sub-array 56B isselected for read operation, bit-lines 114B and 116B are selected, andtheir signals are output to output nodes 74. One of output nodes 74 ismarked as BL and BLB in FIGS. 5 and 6 to indicate that output nodes 74carry signals from the commentary bit-line pairs.

Advantageously, since each of bit-line pairs 114A/116A and 114B/116B isconnected to a half of the SRAM cells in the respective column, the loadon bit-lines and sense amplifier circuit 76 is reduced by a half, andthe differential speed of SRAM cell array 56 may be improved by about 20percent to about 30 percent. It is appreciated that although sub-arrays56A and 56B are connected to different bit-lines, they are still theparts of the same SRAM array since they are connected to the samemultiplexer, and their signals are sensed by the same sense amplifier insense amplifier circuit 76.

Referring again to FIG. 5, a plurality of CVdd lines 78 (also shown inFIG. 6), which carries CVdd power supply, is disposed in SRAM array 56.In accordance with some embodiments of the present disclosure, each ofCVdd lines 78 continuously extends into both sub-array 56A and sub-array56B, and further into jumper structure 58. Accordingly, sub-arrays 56Aand 56B receive the CVdd power supply at the same time, regardless ofwhich of sub-arrays 56A and 56B is selected for (read or write)operation.

FIG. 7 illustrates the layout of metal lines in SRAM cells 10 in SRAMcell array 56 (FIG. 5) in accordance with some embodiments, wherein oneSRAM cell 10 is illustrated as an example. In accordance with someembodiments of the present disclosure, the word-line performance isimproved through double word-line scheme, as shown in FIG. 7. Forexample, word-line 60 is located in a lower metal layer, which may be atM2 level (FIG. 3). Word-line 62 is located in an upper metal layer,which may be at M4 level (FIG. 3). Word-lines 60 and 62 areinterconnected through connection module 64, which includes via 80 atvia_2 level, metal pad 82 at M3 level, and via 84 at via_3 level,wherein the via levels and metal levels are shown in FIG. 3. Through theconnection of connection module 64, word-lines 60 and 62 act as a singlemetal line with an increased thickness, and hence reduced resistance,and hence the RC delay of word-lines is reduced.

Referring back to FIG. 5, word-line connection modules 64 may include64A and/or 64B. Word-line connection modules 64 may be located inside oroutside SRAM cells 10. For example, word-line connection modules 64A arelocated outside of the SRAM cells 10. Word-line connection modules 64B,on the other hand, are inside SRAM cells 10, and may be placed with arepeated pattern, such as every 8, 16, 32, etc. SRAM cells.

FIG. 7 also illustrates that CVss line 86 and/or CVss line 87 are placedin the M2 level (FIG. 3), wherein one or both of CVss lines 86 and 87may be overlapped by word-line 62. Furthermore, CVss lines 86 and 87 areplaced on the opposite sides of word-line 60.

FIG. 8 illustrates SRAM array 56 in accordance with some embodiments ofthe present disclosure. Unless specified otherwise, the connection andthe layout of the components in these embodiments are essentially thesame as the like components, which are denoted by like referencenumerals in the embodiments shown in FIGS. 5 through 7. The details ofthe like components thus may not be repeated herein.

As shown in FIG. 8, in each column of SRAM array 56, there are two CVddlines, namely 78A and 78B, which are disconnected from each other. Eachof CVdd lines 78A and 78B may or may not extend into jumper structure58. CVdd lines 78A and 78B are physically and electrically disconnectedfrom each other, and may carry different power supply voltages withoutaffecting each other. For example, if a row in sub-array 56A is selected(for read or write operation), CVdd line 78A is provided with a fullCVdd voltage in order to operate the selected row. In the meantime,since sub-array 56B is not operated, CVdd line 78B may be provided witha partial power supply voltage lower than the full CVdd voltage or thefull CVdd voltage. The partial power supply voltage may be lower thanabout 50 percent or lower than about 30 percent of the full power supplyvoltage in order to preserve power, depending the intended saving inpower and the designed speed of transition from idle mode (with partialpower) to full operation mode (with full power).

CVdd lines 78A are electrically connected to, and are supplied withpower supply voltages by, CVdd power source 88A. CVdd lines 78B areelectrically connected to, and are supplied with power supply voltagesby, CVdd power source 88B. CVdd power sources 88A and 88B may operateindividually (without affecting and rely upon each other) to provide thedesired power supply voltages to CVdd lines 78A and 78B.

Throughout the description, bit-lines 114A and 116A are also consideredas two separate portions divided from a bit-line, bit-lines 114B and116B are also considered as two separate portions divided from acomplementary bit-line, and CVdd lines 78A and 28B are also consideredas two separate portions divided from a CVdd line.

Referring to FIG. 7, CVdd line 78 (as also shown as 78, 78A, and/or 78Bin FIGS. 5, 6, and 8) extends in the column direction. In accordancewith some embodiments, CVdd line 78 is located in a low metal layer suchas at M1 layer (FIG. 3). Bit-lines 114 and 116 (as also shown as 114A,114B, 116A, and 116B) in FIGS. 5, 6, and 8) may also be in the samemetal layer (such as M1) as CVdd line 78. CVss line 90 may be placed inthe M3 level (FIG. 3) to form a power mesh with CVss lines 86 and 87 atthe M1 level.

The embodiments of the present disclosure have some advantageousfeatures. By separating bit-lines into two portions, each connected tothe SRAM cells in one of sub-arrays, the loading of the bit-lines isreduced, and the bit-line speed is improved. The sensing speed of senseamplifier is also increased. Also, through the use of double word-lines,the resistance of word-lines is reduced, resulting in the reduction ofRC delay. In addition, by separating the CVdd power supplies of thesub-arrays in a same SRAM array, the power consumption is reduced.

In accordance with some embodiments of the present disclosure, anintegrated circuit structure includes an SRAM array including a firstsub-array having a first plurality of rows and a plurality of columns ofSRAM cells, and a second sub-array having a second plurality of rows andthe plurality of columns of SRAM cells. Each of the SRAM cells in theSRAM array includes a first and a second pull-up MOS device, a first anda second pull-down MOS device forming cross-latched inverters with thefirst and the second pull-up MOS devices, and a first and a secondpass-gate MOS device connected to the cross-latched inverters. A firstbit-line and a first complementary bit-line are connected to the firstand the second pass-gate MOS devices of SRAM cells in a column in thefirst sub-array. A second bit-line and a second complementary bit-lineare connected to the first and the second pass-gate MOS devices of SRAMcells in the column in the second sub-array. The first bit-line and thefirst complementary bit-line are disconnected from the second bit-lineand the second complementary bit-line. A sense amplifier circuit iselectrically coupled to, and configured to sense, the first bit-line,the first complementary bit-line, the second bit-line, and the secondcomplementary bit-line.

In accordance with some embodiments of the present disclosure, anintegrated circuit structure includes an SRAM array including a firstsub-array having a first plurality of rows and a plurality of columns ofSRAM cells, and a second sub-array having a second plurality of rows andthe plurality of columns of SRAM cells. Each of the SRAM cells in theSRAM array includes a first and a second pull-up MOS device, a first anda second pull-down MOS device forming cross-latched inverters with thefirst and the second pull-up MOS devices, and a first and a secondpass-gate MOS device connected to the cross-latched inverters. A firstbit-line, a first complementary bit-line, and a first CVdd line are in afirst metal layer and connected to a column of the SRAM cells in thefirst sub-array. A second bit-line, a second complementary bit-line, anda second CVdd line are in the first metal layer, and connected to thecolumn of the SRAM cells in the second sub-array. A first power sourceand a second power source are connected to the first CVdd line and thesecond CVdd line, respectively. A first bridging line and a secondbridging line cross over the second sub-array and connected to the firstbit-line and the first complementary bit-line, respectively. Amultiplexer is connected to the second bit-line, the secondcomplementary bit-line, the first bridging line, and the second bridgingline, respectively.

In accordance with some embodiments of the present disclosure, anintegrated circuit structure includes an SRAM array including a firstsub-array having a first plurality of rows and a plurality of columns ofSRAM cells, and a second sub-array including a second plurality of rowsand the plurality of columns of SRAM cells. Each of the SRAM cells inthe SRAM array includes a first pull-up MOS device and a second pull-upMOS device, and a first pull-down MOS device and a second pull-down MOSdevice forming cross-latched inverters with the first pull-up MOS deviceand the second pull-up MOS device. A bit-line and a complementarybit-line are each physically separated into a first portion and a secondportion, wherein the first portions of the bit-line and thecomplementary bit-line are connected to the first sub-array and not tothe second sub-array, and the second portions of the bit-line and thecomplementary bit-line are connected to the second sub-array and not tothe first sub-array. A multiplexer includes four input nodes, eachconnected to one of the first and the second portions of the bit-lineand the first and the second portions of the complementary bit-line.

The foregoing outlines features of several embodiments so that thoseskilled in the art may better understand the aspects of the presentdisclosure. Those skilled in the art should appreciate that they mayreadily use the present disclosure as a basis for designing or modifyingother processes and structures for carrying out the same purposes and/orachieving the same advantages of the embodiments introduced herein.Those skilled in the art should also realize that such equivalentconstructions do not depart from the spirit and scope of the presentdisclosure, and that they may make various changes, substitutions, andalterations herein without departing from the spirit and scope of thepresent disclosure.

What is claimed is:
 1. An integrated circuit structure comprising: aStatic Random Access Memory (SRAM) array comprising a plurality of SRAMcells forming a first sub-array and a second sub-array; a same senseamplifier connected to both the first sub-array and the secondsub-array; a first bit-line connected to the SRAM cells in a column inthe first sub-array; a second bit-line connected to SRAM cells in thecolumn in the second sub-array, wherein the first bit-line isdisconnected from the second bit-line; and a first bridging metal lineconnected to the first bit-line, wherein the first bridging metal lineoverlaps a portion of second sub-array without connecting to SRAM cellsin the second sub-array.
 2. The integrated circuit structure of claim 1,wherein the first sub-array and the second sub-array in combination forman array, and wherein rows in the first sub-array and rows in the secondsub-array form different rows of the array, and the first sub-array andthe second sub-array share same columns of the array.
 3. The integratedcircuit structure of claim 2, wherein all of columns of the array isconnected to the same sense amplifier.
 4. The integrated circuitstructure of claim 1 further comprising a multiplexer comprising anoutput, and the multiplexer is configured to output signals on one ofthe first bridging metal line and the second bit-line to the output. 5.The integrated circuit structure of claim 4, wherein the first bridgingmetal line are connected between the first bit-line and the multiplexer.6. The integrated circuit structure of claim 1, wherein the firstbridging metal line is in a metal layer different from a metal layer ofthe first bit-line.
 7. The integrated circuit structure of claim 1further comprising: a jumper structure between the first sub-array andthe second sub-array, with the jumper structure having no SRAM celltherein; and connection modules in the jumper structure, wherein theconnection modules connect the first bridging metal line to the firstbit-line.
 8. The integrated circuit structure of claim 1 furthercomprising: a first word-line driver connected to the first sub-array;and a second word-line driver connected to the second sub-array.
 9. Theintegrated circuit structure of claim 1 further comprising: a first CVddline connected to first SRAM cells that are in the first sub-array; afirst power source connected to the first CVdd line; a second CVdd lineconnected to second SRAM cells that are in the second sub-array, whereinthe first CVdd line is disconnected from the second CVdd line; and asecond power source connected to the second CVdd line.
 10. Theintegrated circuit structure of claim 9, wherein the first power sourceand the second power source are configured to apply different powersupply voltages to the first CVdd line and the second CVdd line,respectively.
 11. An integrated circuit structure comprising: a StaticRandom Access Memory (SRAM) array comprising: a first sub-arraycomprising a first plurality of rows and a plurality of columns of SRAMcells; and a second sub-array comprising a second plurality of rows andthe plurality of columns of SRAM cells; a first bit-line connected to acolumn of SRAM cells in the first sub-array; a second bit-line connectedto the column of SRAM cells in the second sub-array; a first powersource and a second power source connected to the first sub-array andthe second sub-array, respectively; a bridging line crossing over thesecond sub-array and connected to the first bit-line; and a multiplexerconfigured to multiplex bit-line signals on the bridging line and thesecond bit-line.
 12. The integrated circuit structure of claim 11further comprising a sense amplifier circuit electrically coupling to,and configured to sense signals on, the first bit-line and the secondbit-line.
 13. The integrated circuit structure of claim 11, wherein thebridging line is electrically disconnected from the second sub-array.14. The integrated circuit structure of claim 11 further comprising afirst power source and a second power source connected to the firstsub-array and the second sub-array, respectively.
 15. The integratedcircuit structure of claim 11, wherein the first bit-line and the secondbit-line physically have a break in between.
 16. The integrated circuitstructure of claim 11, wherein the bridging line is in a metal layerthat is two metal layers different from a metal layer in which the firstbit-line and the second bit-line are located.
 17. The integrated circuitstructure of claim 11, wherein the first power source and the secondpower source are disconnected from each other.
 18. An integrated circuitstructure comprising: a Static Random Access Memory (SRAM) arraycomprising: a first sub-array comprising a first plurality of rows and aplurality of columns of SRAM cells; and a second sub-array comprising asecond plurality of rows and the plurality of columns of SRAM cells; abit-line physically separated into a first portion and a second portion,wherein the first portion of the bit-line is connected to the firstsub-array and disconnected from the second sub-array, and the secondportion of the bit-line is connected to the second sub-array anddisconnected from the first sub-array; and a multiplexer comprising twoinput nodes electrically coupling to the first and the second portionsof the bit-line, wherein the multiplexer is configured to multiplexsignals on the first and the second portions of the bit-line.
 19. Theintegrated circuit structure of claim 18 further comprising a senseamplifier circuit electrically coupling to output nodes of themultiplexer, wherein the multiplexer is configured to forward signals onone of the first portion and the second portion of the bit-line to anoutput node of the multiplexer.
 20. The integrated circuit structure ofclaim 18 further comprising: a first word-line driver and a secondword-line driver connected to the first sub-array and the secondsub-array, respectively.